Modeling of CO2-brine interfacial tension: Application to enhanced oil recovery

Development of reliable and accurate models to estimate carbon dioxide–brine interfacial tension (IFT) is necessary, since its experimental measurement is time-consuming and requires expensive experimental apparatus as well as complicated interpretation procedure. In the current study, feed forward artificial neural network is used for estimation of CO₂–brine IFT based on data from published literature which consists of a number of carbon dioxide–brine interfacial tension data covering broad ranges of temperature, total salinity, mole fractions of impure components and pressure. Trial-and-error method is utilized to optimize the artificial neural network topology in order to enhance its capability of generalization. The results showed that there is good agreement between experimental values and modeling results. Comparison of the empirical correlations with the proposed model suggests that the current model can predict the CO₂–brine IFT more accurately and robustly.     

超临界CO2塑化双基药挤出计量段流动状态的数值模拟

为了掌握超临界二氧化碳(SC-CO₂)塑化双基药在挤出计量段内的流动情况,了解流场内压力、流体速度、剪切速率、剪切黏度等参数的分布与变化情况,使用有限元法的CFD模拟软件Polyflow,对SC-CO₂辅助双基药塑化挤出成型过程中物料在计量段的流动状态进行模拟研究。结果表明,流体压力和剪切黏度都随着工艺温度、注气流率和溶剂比的增大而减小,螺杆转速的提升导致剪切黏度降低,但流体压力却急剧增加。流体外壁面的压力逐级升高,截面处的压力呈现近似环状分布,由机筒内壁面向螺杆表面逐渐减小。截面处的剪切黏度形成以螺杆中心点为圆心的环带状高黏度区域,越贴近机筒内壁和螺杆表面区域的剪切黏度越小,且工艺参数改变不影响剪切黏度的分布规律。流体外壁面的剪切速率随螺杆转速加快而增大,且高剪切速率集中在螺纹处。截面处最大流体速度出现在螺纹附近,紧贴机筒内壁处的流体速度最小,随着远离机筒内壁和螺杆表面流体速度迅速增大,且越靠近螺杆表面及机筒内壁区域的速度梯度越大。     

CO2对高密度水基钻井液性能影响规律及机理分析

准确判断污染物浓度以及其对钻井液影响规律和内在机制是制定有效的CO₂污染防治措施的重要前提,基于酸碱指示变色原理,改进了钻井液中碱度现场定量检测方法,提高测量的准确性和可操作性;采用现场取样跟踪分析以及室内模拟评价相结合的方法,研究了CO₂对高密度水基钻井液流变性和滤失造壁性的影响规律,并从胶体化学的角度出发,开展了CO₂对钻井液黏土胶体颗粒界面Zeta电位、粒度分布以及处理剂吸附影响的实验研究,分析了其作用机理。研究表明,高密度水基钻井液中碳酸根和碳酸氢根存在临界污染浓度,超过此浓度后,钻井液结构黏度和滤失量随其浓度增加而增加;碳酸根和碳酸氢根离子改变了黏土颗粒溶剂化程度和颗粒尺寸,主要表现为黏土胶体颗粒界面电动电势降低、亚微米级粒子减少,粗颗粒增多,黏土颗粒对护胶剂的吸附量减少,导致高密度钻井液黏土颗粒向聚结方向转化并缔合形成三维网络结构的胶凝状态,揭示了宏观性能变化内在机制。      

MoO2/Mo2C Heteronanotubes Function as High‐Performance Li‐Ion Battery Electrode

Instead of carbon, Mo₂C is used to modify the MoO₂ material for the first time. The presence of highly conductive and electrochemical inactive Mo₂C decreases the resistance of the charge transport and enhances the structural stability of MoO₂ nanoparticles upon lithiation and delithiation, ensuring the superior cycling stability and high rate capability of the heteronanotubes. Cycled at 200 and 1000 mA g^?1 for 140 cycles, the discharge capacities of the MoO₂/Mo₂C heteronanotubes remain to be 790 and 510 mAh g^?1, respectively. This work demonstrates the potential of the novel heteronanotubes for application as an electrode material for high‐performance Li‐ion batteries.     

Targeted Synergy between Adjacent Co Atoms on Graphene Oxide as an Efficient New Electrocatalyst for Li–CO2 Batteries

Li–CO₂ batteries are an attractive technology for converting CO₂ into energy. However, the decomposition of insulating Li₂CO₃ on the cathode during discharge is a barrier to practical application. Here, it is demonstrated that a high loading of single Co atoms (≈5.3%) anchored on graphene oxide (adjacent Co/GO) acts as an efficient and durable electrocatalyst for Li–CO₂ batteries. This targeted dispersion of atomic Co provides catalytically adjacent active sites to decompose Li₂CO₃. The adjacent Co/GO exhibits a highly significant sustained discharge capacity of 17 358 mA h g^?1 at 100 mA g^?1 for >100 cycles. Density functional theory simulations confirm that the adjacent Co electrocatalyst possesses the best performance toward the decomposition of Li₂CO₃ and maintains metallic‐like nature after the adsorption of Li₂CO₃.     

纳米二氧化钒薄膜的制备及其特性研究

采用原子层沉积(ALD)方法,分别以VO(OC3H7)3和H2 O2为钒源和氧源,在载玻片基底上沉积钒氧化物薄膜;在还原气氛的管式炉中,对钒氧化物薄膜进行还原退火结晶,进而得到VO2薄膜晶体.通过扫描电镜(SEM)、X-射线衍射(XRD)及X-射线光电子能谱(XPS)研究所制备的钒氧化物薄膜表面形貌、晶体结构以及组分的变化;利用傅里叶红外光谱(FT-IR)对VO2薄膜的红外透射性进行测试分析.结果表明:ALD所制备的薄膜以非晶态V2O5、VO2和V2O3为主;在通以还原气氛(95％Ar,5％H2)并500℃热处理2h后得到以(011)择优取向的单斜金红石纳米VO2薄膜,VO2晶体薄膜相变前后红外透过率突变量较大.     

Influence of inoculum cell density and carbon dioxide concentration on fed-batch cultivation of Nannochloropsis oculata

The marine microalgae Nannochloropsis oculata is a promising source of biofuel because of its high lipid content. For achieving high productivity of oil from microalgae, a high cell concentration before harvesting is beneficial. The present study investigated fed-batch cultures of N. oculata fed with vitamins and nutrient solutions and found that the biomass yield of N. oculata in the fed-batch culture was 1.25 times higher than that in batch culture. Fed-batch cultivation, especially at high illumination, decreased the inhibitory effect of high carbon dioxide (CO₂) concentration on the microalgal growth. The specific growth rate was directly proportional to the light intensity in the CO₂ environment. A light intensity of 40,000 Lux was able to achieve high specific growth rates in fed-batch cultivation at a CO₂ volume fraction of 2%–15%. The tolerance of N. oculata to CO₂ was enhanced by the daily feeding of nutrients in the fed-batch cultivation. At 2% CO₂, a final cell density of about OD₆₈₂ = 11.4 was achieved in the fed-batch culture in 30 days. Furthermore, a cell density of 14.4 g L⁻¹ was obtained by outdoor fed-batch cultivation in 27 days.